Mitsubishi WS-55859 Green tube geometry HELP

I just purchased a ws-55859 mits used and the picture looks great in SD but when I switch to HD the Green has a fairly significant bow on the top edge of the screen (I'm not sure what you call it maybe pincushion). The previous owner said "the bulb" was replaced in it. I'm assuming that it was the green one, and when the tech installed it I think he failed to properly set up the geometry on it. This leaves me with a couple questions. Why would the geometry change from sd to hd? Is there a dial I can hone in myself with a factory service manual or is that out of the question? If that is the case is there any tv repairmen on the central coast of California (San Luis Area) that anybody could reccomend to me?

THanks
Russ

Thanks for the response. I was able to get into the service mode and straighten things out. I should probably have it professionally adjusted, but I'll have to save up some money.